U.S. patent number 5,075,807 [Application Number 07/493,318] was granted by the patent office on 1991-12-24 for magnetic disk device including humidity controller in disk enclosure.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Hideaki Amano, Yoichi Inoue, Katsuyuki Tanaka.
United States Patent |
5,075,807 |
Inoue , et al. |
December 24, 1991 |
Magnetic disk device including humidity controller in disk
enclosure
Abstract
There is provided a magnetic recording device including
recording mediums and an airtight enclosure containing the
recording mediums therein and having a fine breathing hole created
therethrough communicating with the outside thereof, wherein at
least two types of moisture adsorbents composed of a one way type
moisture adsorbent which adsorbs moisture and a reversible type
moisture adsorbent which adsorbs moisture in high humidity and
conversely discharges the same in low humidity are disposed in the
cabinet and used in combination. There is also provided the same
device except wherein gas adsorbents and moisture adsorbents are
used in combination.
Inventors: |
Inoue; Yoichi (Ryugasaki,
JP), Tanaka; Katsuyuki (Ibaraki, JP),
Amano; Hideaki (Odawara, JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
|
Family
ID: |
13158719 |
Appl.
No.: |
07/493,318 |
Filed: |
March 14, 1990 |
Foreign Application Priority Data
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Mar 15, 1989 [JP] |
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1-61002 |
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Current U.S.
Class: |
360/99.15;
236/44R; 360/137; G9B/25.003; G9B/33.043 |
Current CPC
Class: |
G11B
33/1453 (20130101); G11B 25/043 (20130101); G11B
33/1486 (20130101) |
Current International
Class: |
G11B
33/14 (20060101); G11B 25/04 (20060101); G11B
005/012 () |
Field of
Search: |
;360/97.02,97.03,137
;236/44R ;423/210 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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56-13570 |
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Feb 1981 |
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JP |
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58-56270 |
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Apr 1983 |
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JP |
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59-33683 |
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Feb 1984 |
|
JP |
|
61-92492 |
|
May 1986 |
|
JP |
|
61-178790 |
|
Aug 1986 |
|
JP |
|
63-96789 |
|
Apr 1988 |
|
JP |
|
1-48292 |
|
Feb 1989 |
|
JP |
|
Primary Examiner: Psitos; Aristotelis
Assistant Examiner: Garcia; Alfonso
Attorney, Agent or Firm: Antonelli, Terry, Stout &
Kraus
Claims
What is claimed is:
1. A magnetic disk device comprising recording mediums and an
airtight enclosure containing the recording mediums therein, having
a fine breathing hole created therethrough and communicating with
the outside thereof, wherein there are disposed in said enclosure a
gas adsorbent and a moisture adsorbent, said moisture adsorbent
having at least two types of moisture adsorbents including a one
way type moisture adsorbent which adsorbs moisture and a reversible
type moisture adsorbent which adsorbs moisture in high humidity and
conversely discharges the same in low humidity whereby the life of
the magnetic disk device is greatly extended as compared with the
life using only a reversible type moisture adsorbent.
2. A magnetic disk device according to claim 1, wherein a first
case means is disposed in said enclosure for containing said one
way type moisture adsorbent, said first case means having a
diaphragm hole capable of generating a pressure difference between
inside and outside of the first case means, and wherein a second
case means is disposed in said enclosure for containing said
reversible type moisture adsorbent, said second case means having
an opening, and wherein means are provided for filtering dust to
prevent dust from exiting said first and second case means to keep
the interior of the enclosure clean.
3. A magnetic disk device according to claim 1, wherein said fine
breathing hole communicating with the outside is composed of a
valve structure which is opened only when a pressure difference is
produced between the outside and the inside of said enclosure.
4. A magnetic disk device according to claim 1, wherein said gas
adsorbent effectively adsorbs corrosive gases existing in the
atmosphere and is interposed in said enclosure between said
breathing hole and said moisture adsorbents.
5. A magnetic disk device according to claim 1, wherein said gas
adsorbent is also disposed in said enclosure between said breathing
hole and said moisture adsorbent.
6. A magnetic disk device according to claim 4, wherein said gas
adsorbent is disposed mixed with said reversible type moisture
adsorbent.
7. A magnetic disk device according to claim 4, wherein said one
way type moisture adsorbent and said reversible type moisture
adsorbent are mixed together in said enclosure.
8. A magnetic disk device according to claim 1, wherein said one
way type moisture adsorbent and said reversible type moisture
adsorbent are mixed together in said enclosure.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, to recording mediums, and more
specifically, to a magnetic disk device in which thin film magnetic
disk recording mediums as a continuous film are mounted.
2. Related Art
Conventional magnetic disk devices have kept the interior thereof
in a low humidity state by removing moisture flowing thereinto by
using a moisture adsorbent as disclosed in Japanese Patent
Application Kokai (Laid-Open) No. Sho 56-13570, or extended the
life thereof by using only a reversible moisture adsorbent as
disclosed in U.S. Pat. No. 4,831,475. Further, it is generally
known that activated charcoal is used to remove various gases.
The above conventional technologies, however, do not sufficiently
consider an environmental control taking the life of the device
into account or an arrangement of the moisture adsorbent taking the
size of the device into account. In particular, since thin film
magnetic disk recording mediums are generally composed of non-oxide
type magnetic substances, they react with moisture in the
atmosphere or corroded by corrosive gases. Therefore, to increase
the reliability of the recording mediums, moisture and gases flowed
into the device must be sufficiently removed. However, there is a
problem in providing an adsorbent which sufficiently complies with
this requirement and provides a recording medium with reliability.
Further, recently magnetic disk devices have been made smaller in
size and thus the space thereof in which the adsorbent can be
mounted is limited, so that it is difficult to realize a corrosion
resistant environment in the device to satisfy the life length
requirement thereof.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a magnetic disk
device in which an adsorbent is effectively arranged taking into
consideration the characteristics of the adsorbent whereby a
practical amount of the adsorbent for mounting thereof enables
effective adsorption even in the case of rapid temperature
elevation and the device has an increased reliability for a long
duration.
To achieve the above objects, the present invention selects types
of adsorbents which most effectively act in a small magnetic disk
device by classifying corrosive characteristics of an environment
and the characteristics of the adsorbents corresponding to the
corrosive characteristics and arranges them in the device most
effectively in such a manner that: one way and reversible type
moisture adsorbents are used to polar molecules such as moisture of
the substances which exist in the atmosphere as one of corrosive
factors to recording mediums and the like to keep the relative
humidity thereof to a low level for a long time; and a gas
adsorbent such as a mixture of KM.sub.n O.sub.4, H.sub.3 PO.sub.4
and KOH is used to non-polar molecules of corrosive gases such as
SO.sub.2 and H.sub.2 S, and thus the moisture adsorbent and the gas
adsorbent are exclusively used for the respective purposes thereof
and arranged in order of gas adsorbent and moisture adsorbent from
a breathing hole so that adsorbing and removing efficiency is
increased by accelerating gas adsorption reaction.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional view of an example of a magnetic disk
device according to the present invention;
FIG. 2 is a characteristic diagram of the test results of SO.sub.2
density in the device of FIG. 1;
FIG. 3 is a characteristic diagram of the test results of relative
humidity in the device of FIG. 1;
FIG. 4 is a cross sectional view of another example of a magnetic
disk device according to the present invention;
FIG. 5 is a moisture adsorption characteristic diagram of a one way
type silica gel in FIG. 4;
FIG. 6 is a moisture adsorption characteristic diagram of a
reversible type silica gel in FIG. 4; and
FIG. 7 is a diagram of the relationship between relative humidity
and life schematically showing the actions of moisture adsorbents
according to the present invention.
Note that numerals in the figures are designated as follows.
1 . . . enclosure, 2 . . . recording medium, 3 . . . breathing hole
(ventilation hole), 4 . . . adsorbent case, 5 . . . gas adsorbent,
6 . . . silica gel (moisture adsorbent), 7 . . . dust preventing
filter, 8 . . . spiral breathing hole (ventilation hole), 9 . . .
gas adsorbent, 10 . . . reversible type silica gel, 11 . . . one
way type silica gel, 12 . . . adsorbent case, 13 . . . dust
preventing filter, 14 . . . opening, 15 . . . diaphragm hole
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The action of two types of moisture adsorbents will be described
with reference to FIG. 7. It is assumed that a container or
enclosure of a given volume has a fine hole created therethrough,
humid air enters there through the hole, and the container has a
temperature cycle between day and night. An increase in relative
humidity inside the container is caused by two factors, an entrance
of the humid air and a decrease in temperature. In general, a disk
device has a specific humidity (e.g., 70%) at which the life
thereof is terminated and a period of time elapsed until the
humidity is reached is considered to be the life.
To extend the life, it is preferable to use in combination a
moisture adsorbent for adsorbing the entered humid air and a
reversible type moisture adsorbent acting to restrict the variation
range of the relative humidity inside the device. FIG. 7 shows that
the life can be greatly extended by the use of them in combination.
More specifically, it shows that when average humidity has lower
increasing gradients, i.e., the more one way type adsorbent is used
together with the reversible type moisture adsorbent, the more the
life can be effectively extended by the decrease in the variation
made by using the reversible type adsorbent.
Further, corrosive gases such as SO.sub.2, NO.sub.2, H.sub.2 S,
O.sub.2, Cl.sub.2, CH.sub.3 CHO, etc. which exist in the atmosphere
as a corrosive factor to the recording mediums other than moisture
are adsorbed and removed by a gas adsorbent composed of KMnO.sub.4
+H.sub.3 PO.sub.4 +KOH, etc, whereby these gases can be effectively
adsorbed and removed. A gas adsorbent of potassium permanganate,
KMnO.sub.4, known as a substance effectively adsorbing corrosive
gases, reacts with H.sub.2 O with respect to SO.sub.2, etc., as
shown in the following formula, and thus it has higher adsorbing
efficiency in a humid environment.
Further, it produces H.sub.2 O and increases environmental humidity
with respect to H.sub.2 S, etc. at an adsorption reaction, as shown
in the following formula, and thus dehumidification is necessary
after the reaction has been carried out.
When considering either of the reactions, the arrangement of the
gas adsorbent and the moisture adsorbent in this order from a
breathing hole enables moisture to be removed by the moisture
adsorbent after gases have been adsorbed, and thus the contents of
the moisture and gases in the interior of the device can be
effectively lowered. Further, the life of a recording medium and
the like can also be greatly extended by employing a breathing hole
composed of a valve which is opened only when a pressure difference
is produced between the outside and the inside of the device or
employing a ventilation hole composed of a fine tube wound to a
spiral shape so that a dispersing inflow of the above gases and
moisture from the outer air is restricted.
In the present invention, the one way type moisture adsorbent is
defined such that it can adsorb moisture until it is saturated, but
it cannot discharge the adsorbed moisture even if the moisture in
the outer environment is reduced, and this type of the moisture
adsorbent includes, for example, silica gel and silica alumina type
molecular sieves which usually are widely used as a moisture
adsorbent.
Further, the reversible type moisture adsorbent is defined such
that it can discharge or adsorb moisture in accordance with the
change of the moisture contained in an outer environment and this
type of the moisture adsorbent includes, for example, silica gel
having a reversible moisture adsorbing property.
The gas adsorbent is a compound, which reacts with various types of
harmful gases contained in air and injuring the material of a
recording unit of a magnetic disk such as, for example, SO.sub.2,
H.sub.2 S, NO.sub.2, etc. and changes them to solid compounds, and
a substance having a property capable of adsorbing and immobilizing
these gases, and the former includes a compound such as KMnO.sub.4,
H.sub.3 PO.sub.4, KOH, etc. and the latter includes activate
charcoal, molecular sieving carbon, etc. Both of them can of course
be used in combination. When an oxide compound and an alkali
compound are used in combination, they must be separated each other
so that no reaction is caused therebetween. In addition, the gas
and moisture adsorbents may be used in mixture.
The valve arranged as the breathing hole, which is opened when a
pressure difference is produced between the outside and the inside
of the device, includes a valve having a function to be
automatically opened and closed by the pressure difference
produced, and an example of which is a plate-shaped member composed
of rubber and having a cutout created thereto to enable it to be
opened and closed by the pressure difference.
Further, the breathing hole composed of the fine tube wound to the
spiral shape preferably includes a fine tube having a large ratio
of (L/A), where L is a length of the tube and A is a cross
sectional area thereof. Any material can be used for the fine tube
so long as it is inactive to harmful gases, and it is composed, for
example, of plastics or alloy metal.
In the present invention, the gas adsorbent or a case containing it
is disposed in the vicinity of the breathing hole and the moisture
adsorbent or a case containing it is disposed on the above case,
and a dust preventing filter is interposed therebetween, as
necessary.
Thus, a magnetic disk device having a long life can be
provided.
EXAMPLE
Examples of the present invention will be described below with
reference to FIGS. 1 to 6.
FIG. 1 is a cross sectional view of an example of a magnetic-disk
device according to the present invention, wherein recording
mediums 2 and a spindle motor (not shown) for rotating the
recording mediums piled in axial direction thereof are contained in
an enclosure 1 of the magnetic disk device. On the other hand, a
head (not shown) for recording and reproducing information is
mounted on the enclosure. The enclosure 1 is provided with a
breathing hole 3 (ventilation hole) passing from the inside to the
outside thereof. The enclosure 1 does not have any portions
communicating with the outside thereof except the breathing hole,
and thus it is perfectly sealed therefrom. The breathing hole 3 is
composed of a valve (for example, rubber valve) and arranged such
that it is opened only when a pressure difference exists between
the outside and the inside of the device and closed when there is
no pressure difference therebetween. An adsorbent case 4 is
disposed in connection with the breathing hole 3, and a gas
adsorbent 5 mainly composed of potassium permanganate KMnO.sub.4
for adsorbing non-polar gases and a moisture adsorbent (silica gel)
6 for adsorbing polar humid air are arranged from the breathing
hole (ventilation hole) 3 in this order. Dust preventing filters 7
are disposed before and behind the gas adsorbent 5 and the moisture
adsorbent (silica gel) 6 to keep the interior of the enclosure
clean.
With this arrangement, when the magnetic disk device starts or
stops operation, a change of temperature or wind pressure causes
air to flow into the enclosure from the outside thereof through the
breathing hole (ventilation hole) 3. At the time, although harmful
gases simultaneously flow into the enclosure when they exist in the
outside, the gas adsorbent 5 composed of the mixture of KMnO.sub.4,
H.sub.3 PO.sub.4 and KOH can effect an adsorption reaction with the
harmful gases flowing into the device through the breathing hole 3
to remove them. Here, the following adsorption reaction is effected
with respect to hydrogen sulfide H.sub.2 S, acetaldehyde CH.sub.3
CHO, ammonia NH.sub.3, sulfur dioxide SO.sub.2 and nitrogen dioxide
NO.sub.2.
It is found that the reactions in the formulas (4) and (5) are
preferably effected in a highly humid environment and moisture
produced in the reactions in the formulas (1) and (2) is preferably
removed. That is, this means that it is important to cause moisture
to be further adsorbed and removed by the next moisture adsorbent
(silica gel) 6 after the adsorption reaction has been effected. The
results of them experimentally confirmed will be described with
reference to FIGS. 2 and 3.
FIG. 2 is a characteristic diagram of the test results of SO.sub.2
gas density in the device of FIG. 1 and shows the effect thereof,
wherein a horizontal axis shows time and a vertical axis shows
SO.sub.2 density (ppm) in the device, and a solid line shows the
characteristics of the example shown in FIG. 1 and a broken line
shows the characteristics thereof obtained when the position of the
gas adsorbent 5 is replaced with that of the moisture adsorbent 6.
Here, the environment outside the enclosure had a temperature of
25.degree. C., a humidity of 75% RH and a density of sulfur dioxide
of 10 ppm, and the magnetic disk device shown in FIG. 1 and the
magnetic disk device in which the position of the gas adsorbent 5
was replaced with that of the moisture adsorbent 6 in the adsorbent
case 4 in FIG. 1 were placed in the environment and the densities
of the sulfur dioxides in the devices which changed as time passed
were measured. At the time, 1.5 g of the gas adsorbent 5 and 6.0 g
of the moisture adsorbent 6 were placed in each of the enclosures
having a volume of 480 cm.sup.3 and the valve serving as the
breathing hole 3 of each enclosure was forcibly opened to have a
cross sectional area of 0.9 mm.sup.2, and the enclosures were left
in this state. As a result, the first example had a SO.sub.2
density of about 0.75 ppm and approached a saturated state at the
timing when 24 hours had elapsed, whereas the enclosure in which
the position of the gas adsorbent 5 was replaced with that of the
moisture adsorbent 6 had a SO.sub.2 density of about 1.8 ppm which
was twice higher than that of the first example. This proves that
it is effective to adsorb the SO.sup.2 gas by the gas adsorbent 5
before moisture is adsorbed by the moisture adsorbent 6 as shown in
FIG. 1, because moisture is necessary to adsorb the SO.sub.2 gas in
the formula (4).
FIG. 3 is a characteristic diagram of the test results of relative
humidity in the device of FIG. 1 and shows the effect of the
device, wherein a horizontal axis shows time and a vertical axis
shows relative humidity (%) in the enclosure, and a solid line
shows the characteristics of the first example of FIG. 1 and a
broken line shows the characteristics thereof obtained when the
position of the gas adsorbent 5 was replaced with that of the
moisture adsorbent 6. Here, the environment outside the enclosure
had a temperature of 25.degree. C., a humidity of 75% RH and a
density of hydrogen sulfide of 10 ppm as in FIG. 2, and an
experiment as in FIG. 2 was carried out to measure relative
humidity in the device accompanied by the elapse of time. The
results of the experiment show that the hydrogen sulfide H.sub.2 S
having the density of 10 ppm outside the enclosure enables the
first embodiment to more effectively realize a low humid
environment in the enclosure with lower relative humidity (%) as
compared with the device in which the position of the gas adsorbent
5 was replaced with that of the moisture adsorbent 6. This is
because that moisture is discharged when H.sub.2 S is adsorbed by
the gas adsorbent 5 before moisture is adsorbed by the moisture
adsorbent 6 in the formula (1), as shown in FIG. 1.
According to this example, there is an advantage to effectively
remove harmful gases and moisture flowing into the enclosure from
the outside through the breathing hole (ventilation hole) thereof,
and further an advantage to extend the life of the adsorbents
because there is provided the breathing hole composed of the valve
structure which does not breath by diffusion when the magnetic disk
device is at rest.
FIG. 4 is a cross sectional view showing another example of the
magnetic disk device according to the present invention, wherein
metal thin film recording mediums 2 and a means (not shown) for
recording or reproducing information to or from it are contained in
an enclosure 1 of the magnetic disk device. The enclosure 1 is
communicated with the outside thereof only through a spiral
breathing hole (ventilation hole) 8 created therethrough and all
the portions thereof except the hole are perfectly sealed from the
outside. The breathing hole 8 is composed of a spiral fine tube.
Further, an adsorbent case 12 composed of two compartments is
disposed in the enclosure 1. One of the compartments contains a
mixture of KMnO.sub.4, H.sub.3 PO.sub.4 and KOH or a mixture of a
gas adsorbent 9 such as activated charcoal, etc. and moisture
adsorbing and discharging reversible type silica gel (reversible
type moisture adsorbent) 10, and the other thereof contains
moisture adsorbing one way type silica gel (one way type moisture
adsorbent) 11. The former case which contains reversible type
moisture adsorbent has an opening 14 which is large enough to be
capable of instantly adsorbing almost all of the moisture generated
in interior of the device. The latter case has a diaphragm hole 15
a size of which is sufficiently small to generate a pressure
difference between the interior of the case and the outside the
case and interior of the enclosure. In addition, a dust preventing
filter 13 is disposed at the adsorbent case 12 to prevent dust from
being dispersed from the moisture adsorbents 10 and 11. The filter
13 in this example serves as a filter for both an opening 14 and
the diaphragm hole 15.
With this arrangement, an amount D of gases diffusingly flowing
into the magnetic disk device from the outside through the
breathing hole 8 is expressed by the following equation.
where A represents the cross sectional area of the breathing hole,
L represents the path length of the breathing hole, C.sub.out and
C.sub.in represent the gas density outside and inside the
enclosure, respectively, and k is constant. The amount of the
inflow gases is restricted by making the breathing hole spiral so
that it has a smaller cross sectional area A and a longer hole
length L. Further, the gases flowing into the enclosure are removed
by being adsorbed by the gas adsorbent 9, as in the example of FIG.
1. In addition, the usual moisture adsorbing one way type silica
gel 11 is provided to improve the corrosion resistance against
moisture of the recording mediums 2. A diaphragm 15 is interposed
between the case of the one way type silica gel and interior of the
device thereby the life of the silica gel is extended in the same
mechanism as in the case of the breathing hole 8. Although the
absolute humidity in the enclosure can be lowered by the one way
type silica gel 11, there is a possibility that the relative
humidity therein may be increased when the temperature of the
device itself is changed. Thus, the moisture adsorbing and
discharging reversible type silica gel 10 which repeatedly adsorbs
and discharges moisture is used to cope with the temporary increase
in the humidity. The opening 14 has a large enough size as
described before effectively adsorbs moisture in the above case of
relative humidity increase due to temperature increase. The
moisture adsorbing characteristics of the above two types of the
silica gel (moisture adsorbents) 11 and 10 will be described with
reference to FIGS. 5 and 6.
FIG. 5 is a diagram of moisture adsorbing characteristics of the
moisture adsorbing one way type silica gel 11 of FIG. 4, wherein a
horizontal axis shows environmental relative humidity (%) and a
vertical axis shows a moisture adsorbing ratio (%), i.e., a ratio
of the weight of adsorbed moisture to the weight of the silica gel.
As shown in FIG. 5, the conventional one way type silica gel 11 has
an increasing moisture adsorbing ratio, as shown by a solid line,
as the environmental relative humidity is increased and the
moisture once adsorbed thereby cannot be discharged unless the
silica gel is heated.
FIG. 6 is a diagram of moisture adsorbing characteristics of the
moisture adsorbing and discharging reversible type silica gel 10 of
FIG. 4 as in the above, wherein a horizontal axis shows
environmental relative humidity (%) likewise and a vertical axis
shows a moisture adsorbing ratio (%), i.e., a ratio of the weight
of adsorbed moisture to the weight of the silica gel. As shown in
FIG. 6, the moisture adsorbing and discharging reversible type
silica gel 10 has an abruptly increasing moisture adsorbing ratio,
as shown by an arrowed solid line, as the environmental relative
humidity is increased. When, however, the environmental relative
humidity is lowered from 60% to 40%, the silica gel 10 discharges
once adsorbed moisture and the moisture adsorbing ratio thereof is
more gradually lowered as shown by the arrowed solid line, and thus
usually a constant humidity from 50 to 80% can be kept.
In this example, a mixture of 1.5 g of a gas adsorbent and 0.2 g of
reversible silica gel 10 was disposed in a disk enclosure having a
volume of 480 cm.sup.3 as in the first example, and 2 g of one way
silica gel 11 was additionally disposed therein. The disk device
was left in the environment having a temperature of 25.degree. C.,
a relative humidity of 75% RH and a density of sulfur dioxide
SO.sub.2 of 10 ppm as in the first example. As a result, a relative
humidity in the enclosure was as low as 55% when 24 hours had
passed. In addition, this relative humidity exhibited a tendency
shown in FIG. 7 even if time further passed, whereby a lower humid
environment could be kept for a long time regardless of that a
total amount of the silica gel was less than that of the first
example.
The case of the reversible silica gel 10 is provided with a
structure having an opening 14 sufficiently large to be able to
instantly adsorb moisture when the humidity inside the device
rapidly increases. In other words, the opening of the case has no
diaphragm. As described above, the use in combination of the two
types of the moisture adsorbing and discharging reversible type
silica gel (moisture adsorbent) 10 and the moisture adsorbing one
way type silica gel (moisture adsorbent) 11 enables the interior of
the magnetic disk enclosure to be kept in a low humidity state with
a very small amount of the moisture adsorbents. Further, as
described with reference to the first example of FIGS. 1 to 3, the
characteristics of the gas adsorbent 9 is more effective when more
humid air exists, and thus when it is mixed with the moisture
adsorbing and discharging reversible type silica gel 10 which
sometimes discharges moisture and used in the same compartment in
the adsorbent chamber 12, the gas adsorbing efficiency of the gas
adsorbent 9 can be improved.
According to the present example, the use in combination of the one
way type moisture adsorbent and the reversible type moisture
adsorbent enables the interior of the disk enclosure to be kept in
a low humidity state for a very long period. Further, since harmful
gases can be effectively removed, the environment in which the
reliability of the recording mediums is improved can be
realized.
The gas adsorbent in the above examples may be a mixture of
KMnO.sub.4, H.sub.3 PO.sub.4 and KOH, activated charcoal, or
molecular sieving carbon. The moisture adsorbing one way type
adsorbent may be silica gel, silica alumina type molecular sieves
or the like. Further, the moisture adsorbing and discharging
reversible type moisture adsorbent is not limited to the silica
gel. Furthermore, the breathing hole or the ventilation hole is not
limited to the valve structure composed of the elastic member which
is opened only when a pressure difference exists between the inside
and the outside of the enclosure and usually closed, the spiral
breathing hole, or the like.
According to the present invention, since the environment in the
magnetic disk enclosure can be kept in a low humidity state for a
long period by the use in combination of the one way and reversible
type moisture adsorbents, high reliability can be achieved in that
no corrosion is caused to the thin film disk recording mediums and
the like. Further, harmful gases can be effectively removed.
* * * * *